Explosive



Patented Nov. 18,, 1941 EXPLOSIVE Charles Samuel Hallett, Bath, EnglandNo Drawing. Application July 22, 1940, Serial No. 346,868. In GreatBritain July 4, 1939 8 Claims. (on. 52-18)- This invention relates tothe manufacture of explosives. and in particular to the production ofhigh explosives suitable for use in coal or other mines.

The explosives heretofore generally employed for use in coal mines fallwithin what is known as the low density class and usually comprisecompositions consisting of ammonium nitrate, carbohydrates or wood-meal,a nitro-compound and a cooling agent. of the ingredients just mentioned,ammonium nitrate and nitro-compounds are used to a large extent in themanufacture of explosives for military purposes, so that, in view ofpossible non-availability or severe restriction of the supply ofnitrates or nitrocompouncls, it is desirable to have industrialexplosives in which the particular ingredients just mentioned are notpresent.

Industrial explosives containing chlorates have been proposed, but owingto their great sensitivity and liability to decomposition andspontaneous combustion in storage, especially in the presence ofmoisture, they are not permitted explosives.

Some coal mine explosives falling within the low density classification(designed to bring the coal down in large lumps as distinct fromtheshattering eiiect of high explosives) cannot be relied on to beflameless because exploding by combustion is productive of flame andonly a small percentage of cooling elements (about 13%) can be employedwithout preventing explosion.

Potassium perchlorate is much less sensitive than potassium chlorate andis stable even in the presence of moisture; in the case, however, ofprevious proposals for the production of perchlorate explosives, it hasbeen found necessary. in consequence of the greater insensitivity of theperchlorates as compared with the chlorates and the substantialproportion of cooling salts necess sary for a coal mine explosive, touse the former in conjunction with ultra-compounds, since otherwise theperchlorate mixtures were'found The present invention has the foregoinggeneral objects and particularly the production of perchlorateexplosives containing no nitrates or nitro-compounds and of the requiredefliciency and safety in use and storage. For this purpose, theexplosive composition according to the present invention comprises amixture of a perchlorate of an alkali or alkali earth metal with acarbonaceous substance, such as for example coal tar pitch, bitumen,coal dust, coke, charcoal, graphite or lampblack, small proportions ofsensitizing agents such as a sugar and a bichromate not exceeding 6% ofthe total, together with a salt, such as, for instance, sodium chloride,which acts as a cooling agent and is in excess of 20% of the total.

As an example of apreferred explosive according to the invention theremay be mentioned one of the following composition: 58 to 60 partspotassium perchlorate, 10 to 12 parts coal tar pitch, 3 parts sugar, 1part potassium bichromate, and 26 parts sodium chloride. It will be seenthat the sensitizing agents do not total more than 4% or approximatelyso within the limits of the alternative proportions of the otherconstituents set forth, while the coolant amounts to 26% orapproximately so according to the proportions of the other ingredientswithin the limits set forth.

In manufacturing the composition, it is desirable first to mix togetherthe four soluble ingredients with a small proportion of water to ensure"complete safety during The amount of water may be in the region ofapproximately 15% by weight, suflicient to make the mixture thoroughlydamp. Then, when these ingredients have been thoroughly incorporatedtogether, the pitch is added in a powdered condition. the mixing beingcontinued until a completely homogeneous mixture is obtained. Theresidual water in the mixture may then be expelled by gently heating itto a temperature of about 40 C.

The improved explosives according to the present invention areefficient, safe and cheap to manufacture and are designed to be ofparticular use in coal mines, where safety is the primary consideration.The new explosive compositions are insensitive to friction to asubstantial extent, but can be detonatedin' the usual manner of highexplosives by the use of appropriate detonators. pounds, theirmanufacture can be carried out more cheaply than that of explosivescontaining 555 such compounds.

As they do not contain nitro-com- I claim:

1. An explosive composition consisting of 58 to 60 parts potassiumperchlorate, 10 to 12 parts coal tar pitch, 3 parts sugar, 1 partpotassium bichromate and 26 .parts sodium chloride.

2. An explosive composition consisting of 58 to 60 parts potassiumperchlorate, 10 to 12 parts carbonaceous substance, 3 parts sugar, 1part potassium bichromate, and 26 parts sodium chloride.

3. An explosive composition consisting of 58 to 60 parts potassiumperchlorate, 10 to 12 parts carbonaceous substance containing uncombinedcarbon, 3 parts sugar, 1 part potassium bichromate, and 26 parts sodiumchloride.

4. An explosive composition consisting of a mixture of 58 to 60 parts ofperchlorate of the group consisting of alkali metals andalkaline earthmetals, 10 to 12 parts of a carbonaceous substance, less than 6 partsof. a sensitizing agent comprising sugar and bichromate, and alkalimetal chloride in amount upwards of 20 parts but insuflicient to renderthe mixture inexpl'odable.

- 5. An explosive composition consisting of a mixture of 58 to 60 partsof perchlorate of the group consisting of alkali metals and alkalineupwards of 20 per cent of the total but insufilcient to render themixture inexplodable.

'7. An explosive consisting of a mixture in predominating quantity of aperchlorate of the group consisting of alkali metals and alkaline earthmetals, a carbonaceous substance containing uncombined carbon, asensitizing agent comprising sugar and bichromate in an amount notexceeding 6 per cent of the total, and alkali metal chloride in anamount upwards of 20 per cent of the total but insuflicient to renderthe mixture inexplodable.

8. An explosive consisting of a mixture in predominating quantity of aperchlorate of the group consisting of alkali metals and alkaline earthmetals, a carbonaceous substance, a sensitizing agent comprising sugarand bichromate in an amount not exceeding 6 per cent of the total, andalkali metal chloride in an amount of substantially 26 per cent of thetotal.

CHARLES SAMUEL HALLE'I'I.

